This invention relates to an improvement on a solenoid valve for controlling the flow of fluid. The fluid flow control solenoid valve comprises a valve body having a passage for fluid and a valve seat disposed in the passage; a valve member disposed opposite to the valve seat; and an electromagnetic driver for actuating the valve member. The electromagnetic driver has a yoke, a coil and a movable core and moves the valve member by an output shaft connected with the movable core to control the flow rate of fluid according to the stroke of the valve member.
A solenoid valve of the aforementioned type is described, for example, in U.S. Pat. No. 3,757,263 granted to Saarem, et al, on Sept. 4, 1973.
There are two types of solenoid valve for controlling the flow of fluid. One is a proportional type which controls the stroke of the electromagnetic driver non-stepwise or continuously to provide the fluid flow rate which is proportional to the electric current input to the electromagnetic driver. The other is an on-off type which simply blocks the flow of fluid. In either type, it is necessary to secure the electromagnetic driver to the valve body.
In the solenoid valve of known construction, the electromagnetic driver has a mounting portion projection and this projection is threaded into the valve body. Thus, it is difficult to accurately align the center of the output shaft of the electromagnetic driver with the center of the valve member, with a resultant off-centered load acting upon the moving parts such as the movable core of the electromagnetic driver and the valve member. Although the off-centered load does not noticeably deteriorate the operating characteristic of the on-off type of the solenoid valve, it does have a great adverse effects on the operating characteristic of the proportional type and produces a hysteresis in the flow rate control characteristic.
Furthermore, in the known construction, since the electromagnetic driver is screwed into the valve body, the position of the terminals of the electromagnetic driver is not constant and varies from valve to valve. This makes it troublesome to wire the terminals with external electrical equipment. Especially in the proportional type, it is almost impossible to bring the terminals to a predetermined position for all valves, since the control characteristic is adjusted by giving the electromagnetic driver further reverse turns to change the force of the spring.